Apparatus for applying signals to electrodes of an electron tube



July 19, 1955 L. PENSAK 2,713,604 APPARATUS FOR APPLYING SIGNALS TOELECTRODES OF AN ELECTRON TUBE Filed March 15, 1952 3 Sheets-Sheet l 5%"away/7' Edi/7019779! ATTORNEY July 19, 1955 PENSAK 2,713,604-

APPARATUS FOR APPLYING SIGNALS T0 ELECTRODES OF AN ELECTRON TUBE FiledMarch 15, 1952 3 Sheets-Sheet 2 ATTORNEY July 19, 1955 PENSAK 2,713,604

APPARATUS FOR APPLYING SIGNALS To ELECTRODES OF AN ELECTRON TUBE FiledMarch 15, 1952 s Sheets-Sheet s ATTORNEY aired States Patent 2,7 l fifilPatented duly 159, "i955 2,713,504 APPARA'HUS FUR APPLYING SIGNALS T0ELECTRGEDES (3F AN ELECTRON TUBE Louis Pensak, Princeton, N. 5.,assignor to Radio Corporation of America, a corporation of DelawareApplication March 15, 1952, Serial No. 276,835

6 Claims. (Cl. 178-5.4)

This invention relates to age waves to electrodes of an electrondischarge device in such manner as to minimize the loading eiTect ofinterelectrode or other stray capacitance.

In some types of color kinescopes employed in television the intensityof the selected component color re- :1?

produced is controlled by the application of video to an appropriateelectrode or electrodes. In other types of color kinescopes one oranother selected component color is produced in accordance with theinstantaneous signals magnitude of a color selection signal that isapplied to associated with each of t e electrodes. Because collectorsare smaller than the electrodes, their interelectrode capacitance islower than the interelectrode capacity of electrodes so that thecollectors do not load the source of the voltage waves excessively. Thecapacitive coupling between the collectors and their correspondingelectrodes is extremely small so that the electrodes are effectivelyisolated from the collectors and the sources of voltage waves. Oneconvenient way of coupling the electrodes to the collectors is by thesecondary electrons produced when portions of the electrode structure ofwhich the electrodes form at least a part are bombarded by a beam ofelectrons.

The manner in which the above objective is attained by this inventionmay be more clearly understood after a detailed consideration of thedrawings in which:

Figure 1 is a side view of a target embodying the principles of thepresent invention and employed in a color kinescope of the type whereinvideo signals are applied to the electrodes of the target so as tocontrol the intensity with which different color phosphors of a phosphorscreen luminesce.

Figure 2 is a view of the target shown in Figure 1 taken along a sectionAA of Figure 1;

Figure 3 illustrates by block diagram an arrangement that may beemployed in conjunction with a target such illustrated in Figures 1 and2;

Figure 4 is a top view of a means for connecting selected ones of theelectrodes in desired sources of voltage waves;

Figure 5 is a front view of Figure 4;

Figure 6 illustrates the circuitry employed in accordapparatus forapplying volthe invention will now be described as applied to a colorkinescope of the first type mentioned above wherein component colors.

S. patent application bearing Serial No. 138,088 filed on January 12,1950, in the name of Zworykin.

so as to be parallel to the lines of the raster scanned by the electronbeam. in between successive pairs of ribs 3 are grooves 33, 3G, 3R,strips 4G, 4B, 4R, are mounted at the bottoms of the grooves 33, 3G, 3Retc. so as to be in contact with the metallic strip 2. The strips 4B,4G, 4R, etc. that phosphor strips 8B.

in order that the drawing of Figure 1 may be clearly understood noconnections are shown for coupling the various signals to theircorresponding grid members.

The manner in which the various grid electrodes 58, 5G, and SR arecoupled to their respective sources of video signals so as to reduce thecapacitive loading of these sources in accordance with the principles ofthis invention is illustrated in Figure 2. Each pair of grid electrodes5B are electrically connected together by a loop of conto pick up anyelectrons emitted by the loops 913, 9G and 9R respectively. eachcollector plate picks up only those electrons from the adjacent loop.All of the collector plates 10B are electrically connected to a sourceof blue video signals 13, all of the collector plates 10G areelectrically connected to a source of green video signals 12, and allthe collector plates 10R are connected to a source of video signals 11.

Secondary electrons are emitted by the loops 93, 9G and 9R in responseto bombardment by an auxiliary beam of electrons 14 that is caused toscan in vertical synchronism with a main beam 15 in a manner to bediscussed below. The present discussion relates to the effect of theauxiliary beam 14 and points out how the use of such a beam decreasesthe capacitive loading of the sources 11, 12 and 13 by a large amount.If the loops 98, 9G, 9R that connect the pairs of grid electrodes 58, Gand SR respectively are comprised of material that is capable ofemitting secondary electrons, those electrons will be picked up by thecorresponding collector plates B, 106 and 10R. The electron couplingthus introduced causes the loops to assume the same potential as thecorresponding collector plates and therefore to have the same potentialvariations as the video signals supplied by the sources coupled to theplates. The capacitive loading of the sources 11, 12 and 13 is reducedmaterially by a combination of two factors. In the first place the totaldistributed capacitance of all the collector plates connected to any oneof the sources is much less than the distributed capacitance of the gridelectrodes that in previous arrangements were connected to any one ofthe sources. In the second place, only the distributed capacitance of arelatively small number of the control electrodes 5 is added to thedistributed capacitance of these 601180101 plates. The number of controlelectrodes Whose distributed capacitance is thus added depends upon thesize of auxiliary beam 14. If this beam is such as to encompass threesuccessive grid loops 9B, 9G and 9R, then the source 13, for example, iscapacitively loaded only by the sum of all the distributed capacitanceassociated with the different collector plates 18B, and in addition onlythe distributed capacitance of one set of grid electrodes 5B. The sameis true for the sources 11 and 12. Thus the essence of invention lies inproviding means for coupling only a relatively small number of thecontrol grid electrodes to any one of the sources, the coupling meansitself having a much smaller total interelectrode capacitance than thetotal interelectrode capacitance of all the control electrodes thatwould normally be coupled to any one source.

The particular size of cross sectional area of the main beam that scansa raster on the metallic sheet 2 of Figure 1 depends upon the manner inwhich the final image is to be formed and upon the type of signalssupplied by the sources 11, 12 and 13. For example, if the image is tobe built up from a series of parallel color lines the main beam 15 mayhave a cross sectional area equal to the width of one of the strips 413,4G or 41R, and may be caused to scan along these strips in sequence.Thus even though the signals provided by the sources 11, 12 and 13 arecontinuous, only those signals from one of the sources will control thenumber of electrons reaching a given phosphor strip 83, 8G or 8R duringany one line scansion. On the other hand, if the cross sectional area ofthe main beam 15 is sufficient to encompass at least three strips, thatis 413, 4G and 4R, the signals supplied by the sources 13, 12 and 11could be of the line sequential type. In this case the blue videosignals supplied by the source 13 would permit secondary electrons fromthe strip 4B to reach the blue phosphor strip 83, and the signalssupplied by the sources 11 and 12 would prevent any electrons fromreaching the phosphor strips 86 and SR. During the next line scansionthe main beam 15 would not scan the top strip 4B but would encompass thenext 3 lower strips that is 4G, 4R and the next lower strip 4B.

The physical arrangement is such that If it is desired to reproducegreen light during this next line scansion, the green video signals fromthe source 12 permit electrons to reach the uppermost green phosphorstrip 8G and the sources 11 and 13 of red and blue video signalsrespectively would prevent any secondary electrons from reaching thecorresponding phosphor strips.

If it is desired to build up the final color image from a series ofdifferently colored dots of light the signal supplied by the sources 11,12 and 13 could be of the elemental sequential type and the main beam 15could be of sufficiently large diameter to encompass at least threesuccessive strips 4B, 4G and 4R. Other combina' tions of beam size andthe type of signals provided by the sources 11, 12 and 13 could bedevised by one skilled in the art so as to build up the final colorimage in any desired manner. The particular size of the main beam 15 isnot important to the practice of the present invention. In the abovediscussion it is only intended to indicate other various ways in whichthe entire apparatus may be used.

Figure 3 illustrates a type of cathode ray tube and circuitry that maybe employed in conjunction with the target structure shown in Figures 1and 2 so as to achieve the desired results and advantages of the presentinvention. The color video signals may be detected by any suitablereceiver and applied to a target structure 21 via leads 22, 23 and 24.The details of the target structure 21 are the same as those illustratedin Figures 1 and 2. The cathode ray tube 25 in which target 21 ismounted is equipped with a standard gun 27 and a standard yoke 28 thatcauses the beam emitted by the gun 27 to scan a raster on the targetfashion. Between the gun 27, the yoke 28 on the one hand and the target21 on the other is another electron gun 29 that is mounted so as todirect an auxiliary beam of electrons indicated in cross section by thenumeral 14 in Figure l to one edge of the target 21. The verticaldeflection of this beam is controlled by deflection plates 30 andfocussing of the beam is brought about by a coil 31. Owing to the factthat the two guns are not the same distance from the focussing fieldestablished by the coil 31, one will be in focus at the target 21 andthe other will be slightly out of focus. The current in the coil 31 isadjusted so as to focus the beam from the gun 27 from the target 21 andto cause the beam from the gun 29 to be slightly defocussed at thetarget 21. This means that the auxiliary beam will cover at least one ofthe loops 9 and in the practical case will cover more than one. As willreadily be understood by those skilled in the art, the relative sizes ofthe cross sectional areas of the main and auxiliary beams can becontrolled by changing the cathode potential. The synchronizing signalsare separated from the output of the receiver 20 by a standard syncseparator 32 and are applied to a horizontal sweep circuit 33 and avertical sweep circuit 34 of conventional design. The output of thehorizontal sweep circuit 33 is applied via an amplifier 35 to thehorizontal deflection coils in the yoke 28. The output of the verticalsweep circuit 34 is applied via an amplifier 36 with vertical deflectioncoils in the yoke 28. These connections and circuits are standard.Inasmuch as the auxiliary beam emitted by the gun 29 is to scan only ina vertical direction, the yoke 30 is supplied with signals from only thevertical sweep circuit 34 via an amplifier 37. The gain of the amplifier37 is so adjusted with respect to the gain of the amplifier 36 that thesame vertical sweep voltages may cause the auxiliary beam emitted by thegun 29 to scan the same vertical distance at any given time as the mainbeam emitted by the gun 27.

Figures 4 and 5 illustrate another means whereby an auxiliary beam ofelectrons may be caused to land upon a few of the loops at any giveninstant. It would be apparent to those skilled in the art that thenumber of secondaries emitted in response to the auxiliary beam 21 in anormalof the type illustrated in Figure 2 will be proportional to thedensity of the beam. Whereas it is true that the electron density of thebeam can be increased by increasing the voltage difference through whichthe beam passes, it is also true that the number of secondaries maximumin the neighborhood Any further increase in the density of the beamcurrent that arrives at the target the electron gun and the target. Ingeneral, the greater the distance the greater must be the voltagedifferential to obtain a given electron density. However, as notedabove, an increase in voltage beyond a predetermined amount causes thenumber of secondaries emitted to be reduced.

In Figure 4 an arrangement is shown whereby the distance through whichthe beam passes is greatly reduced so as to permit an optimum voltage inthe order of 500 volts to be used. The target may be similar to thatshown in Figures 1 and 2 and is generally indicated parallel to one edgeof the target 4%). An accelerating anode 42 is mounted parallel to therod 41 and has a slit 43 extending the full length of the rod 41. Anystand ard means may be employed for heating the cathode 41 shapedeflection plates 44 of the slit 4-3 and ribbon. The

beam of electrons emerging from The ribbon beam 46 that is placed 45 andthe target view of the Figure 4 AA, the mask 46 has a diagonal slot ofelectrons then encounters a mask between the deflection plates 44 and 47cut through it. lector electrodes 14 are placed in such manner that anyelectrons passing through this slit 47 may strike It can be seen that ifa voltage tion plates 44 and 45 that deflects the beam left that thebeam will pass through any suitable receiver 51 and applied via leads52, 53 and 54 respectively to different groups of collector electrodesin the target 40. In view of the fact that the target 40 is illustratedin detail in Figures 1 and 2, these details are omitted in and focussedby a to scan a raster on the emerging through the slit 47 of The beam isthe loops associated with the grid electrodes that control main beam ofelectrons.

Figures 7, 8 and 9 illustrate the manner in which the invention reducesthe capacitative loading of a source of keying signals that are appliedto color selection electrodes. Further details of the tube employed inthis arrangement may be found in the U. S. Patent No. 2,446,791 issuedon August 10, 1948, in the name of Alfred C. Schroeder. Only thosedetails of this tube that are essential to the application of thisinvention to this type of tube are shown. In this case the target iscomprised of a sheet 70 75' are equal, electrons passing through thegrid structure strike the green phosphor strips as indicated by a path'78.

When the lead 74 is made positive lead 75 these grid pair so as redphosphor. Those electrons passing through the next lower adjacent pairof grid Wires also strise a red phosphor but are deflected downwardalong a path 81.

strike a blue phosphor, and the electrons passing through as to strike ablue phosphor.

The target structure just described in Figures 7 and 8 components thatrepresent the color information, a burst of energy that represents astandard color and the standard type of scanning sync signals. Thescanning sync signals are separated from the output of the receiver 85by any standard sync separating apparatus 86 and applied to vertical andhorizontal sweep circuits 87 and 88 respectively. The outputs of thesesweep circuits are applied to a deflection yoke 89 via amplifiers 90 and91 so as to cause the electron beam projected by an electron gun 92 toscan a raster on a target 93. The target 93 is of the type set forth indetail in Figures 7 and 8. The burst of color synchronizing signals areseparated from the rest of the signals by a burst separator 94 andapplied to a color switching circuit 95 that is connected to the leads74 and 75 so as to control the relative voltages applied to thedifferent groups of grid wires 71 and 72. Assuming that the images areto be reproduced with three selected component colors, a continuousthird harmonic of the burst frequency is generated by a harmonicgenerator 96, and the phase of the continuous harmonic is controlled bya phase control device 97. The video signals supplied by the receiver 85are combined in an adder 98 with the output of the phase control device97 and applied to a control grid (not shown) in an electron gun 99 thatprojects the main beam of electrons. The cathode (again not shown) ofthe gun 99 may be biased so that the main beam of electrons is cut offduring the peaks of the continuous harmonic wave supplied by the phasecontrol device 97. The phase control device 97 is adjusted so that thegun 99 is turned on whenever its beam is centered on a single colorphosphor by the voltages supplied by the grid groups 71 and 72. A gun10%) serves to direct an auxiliary beam of electrons towards the target93 and both beams pass through a focussing field established by a coil101. The current in the focussing coil 10% is adjusted so as to sharplyfocus the main beam projected by the electron gun 99 at the target 93and to slightly defocus the auxiliary beam projected by the gun 190. Theauxiliary beam is deflected in the vertical direction in synchronisrnwith the vertical deflection of the main beam by application of theoutput of the vertical sweep circuit 37 to a set of deflection plates1&2 through which only the auxiliary beam passes.

What is claimed is:

1. Apparatus for applying voltage waves to a plurality of electrodestructures having a relatively large interelectrode capacity in suchmanner that the capacitative loading effect of the electrodes on thesource of the voltage waves is minimized comprising in combination anelectron gun for producing a beam of electrons, means to cause said beamto scan successively over portions of each of said electrode structuresso as to cause said portions to emit secondary electrons, sep aratecollector plates, each of said plates being mounted so as to collectsecondary electrons from the portion of one of said electrodes struck bysaid beam of electrons, and means for coupling a plurality of saidcollector plates to said source of voltage waves so that said voltagewaves are applied to particular ones of said electrodes only when saidparticular electrodes are emitting secondary electrons.

2. In conjunction with a cathode ray tube wherein a source of voltagewaves is to be connected to a plurality of electrodes, and wherein theinterelectrode capacity of said electrodes is large, apparatus forreducing the loading effect normally produced on said source by saidinterelectrode capacity comprising in combination separate means forcollecting secondary electrons from a portion of each of saidelectrodes, said means having less interelectrode capacity than saidelectrodes, said means being coupled to the source of voltage waves,said means being arranged with respect to said electrodes in such mannerthat the voltages applied to said means are established on thecorresponding ones of said electrodes only when said portions of said 1-so as to control the electrodes are emitting secondary electrons, andmeans for scanning said portions of the electrodes with electrons insuch manner that said electrodes successively emit secondary electrons.

3. Apparatus for selectively applying voltage waves to one or more of aplurality of electrodes in such manner that the loading effect of theinterelectrode capacity of said electrodes on the source of said voltagewaves is materially reduced, comprising in combination a set ofauxiliary electrodes, each of said auxiliary electrodes being adapted tobe coupled to one of said electrodes, said auxiliary electrodes havingless inherent capacity than said electrodes, means for coupling saidvoltage waves to said auxiliary electrodes, and electron dis- 1 chargemeans for selectively coupling at least one of said auxiliary electrodesto its corresponding electrode at any given time so that the voltagewaves are applied to less than the whole number of said electrodes.

4. Cathode ray tube apparatus comprising in combination an evacuatedenvelope, a target having a plurality of segregated areas adapted toemit electrons from one side when struck by light from another, meansadapted to direct a beam of uniform intensity toward said target, ascreen, different areas of said screen being adapted to emit light of adifierent selected component color when struck by moving electrons,means for causing said beam of electrons to scan a raster on saidtarget, a grid structure comprised of a plurality of groups of membersmounted between said target and a said screen, a collector positionedwith respect to each grid member so as to collect any secondaryelectrons emitted from a portion thereof, said collectors having lessinherent capacity than the corresponding grid members, one group of saidgrid members being positioned flow of electrons from certain areas ofsaid target to areas of said screen that luminesce with light of oneselected component color, another group of said grid members beingpositioned so as to control the flow of electrons from other areas ofsaid target to other areas of said screen that luminesce with adifferent selected component color when struck by electrons, means forapplying video signals represent ing the intensity variation of one ofsaid selected component colors to the collectors associated with thegroup of grid members adapted to control the flow of electrons from thetarget to the areas of the screen that luminesce in the same selectedcomponent color, means for applying signals representing a differentselected component color to the collector associated with a group ofgrid members that control the flow of electrons from said target toareas of said screen that luminesce in said other selected componentcolor when struck by electrons, means for generating another beam ofelectrons, means for causing said other beam of electrons to strike theportions of said grid members that are mounted so that secondaryelectrons emitted therefrom are gathered by said collectors, and meansfor causing said latter beam to strike said portion at a time when thefirst mentioned beam is striking the target at points where the samegrids control the flow of electrons to the screen.

5. Apparatus for reproducing images in color comprising in combination,a cathode ray tube having a target, different segregated areas of saidtarget being adapted to luminesce with light of a different selectedcomponent color, an electron gun adapted to direct a beam of electronstoward said target, means adapted to cause said beam to scan a raster onsaid target, a grid structure mounted in said tube, said grid beingcomprised of a plurality of groups of members, said groups of membersbeing so positioned with respect to said target that the electrons fromsaid gun strike segreated areas of said target determined by thevoltages applied to said groups of grid members; a plurality of electroncollectors, each collector being mounted so as to gather secondaryelectrons from a portion of a particular gnd member, the collectors thusassociated bers in synchronlsm with the scanning of said other electronbeam.

6, Apparatus as described in claim 5 wherein a source of color switchingsignals is connected between said groups of grid members.

References Cited in the file of this patent UNITED STATES PATENTSSchroeder Aug. 10, Chew Nov. 14, Oklicsanyi Dec. 5, Sziklai Feb. 26,Rose Nov. 11, Bradley July 7, Weimer Aug. 25,

